Utility trailers are used to provide additional hauling capacity to standard automobiles and light trucks. They often connect to such a vehicle using a hitch, such as a conventional ball hitch. An electrical connection, typically through a connection to the brake light power source, is employed to enable brake lights at the rear of the utility trailer.
Conventionally, utility trailers have a single axle on which the trailer's wheels are mounted. By connecting to the hitch, the trailer is then supported at three points (the hitch and each of the wheels.) This leaves the trailer relatively level and stable. The axle is typically mounted to the trailer using a set of leaf springs. This provides a durable suspension system that effectively spreads the weight load widely over the chassis of the utility trailer.
On acknowledged problem with the use of leaf springs is their inability to vary the stiffness of the suspension in response to differing loading weights. To address this issue, pneumatic or air suspensions have been employed. The leaf spring is replaced by a compressible air bladder that can be variably inflated to different pressures. The air pressure in the bladder can be varied to accommodate different loads, and to adjust the stiffness of the suspension. One example of such a system is provided in U.S. Pat. No. 6,086,276, which discloses the use of an inflatable air bladder to act as a dampener for a partial axle.
The use of an air bladder also offers the ability to increase the functionality of a trailer by allowing the bed of the trailer to be lowered through deflation of the bladder. This effectively provides the ability to have the trailer “kneel” to allow easier access.
Despite the existence of air suspension trailers, the market for all small trailers is typically tilted towards sales of the lower cost leaf spring suspension trailers. Often a leaf spring suspension trailer is the first trailer that a person will purchase, and only when a second trailer is needed does a person consider buying an air suspension trailer
As a well-maintained trailer often lasts a long time, many people who might be interested in the functional advantages of an air suspension system do not consider purchasing a new trailer because the existing trailer is fully serviceable.
Various air-suspension systems exist, including those provided by Dexter Axle, whose Airflex™ system is intended for use by trailer assembly and sales companies to use in air-suspension trailers. In conventional air-suspension systems an expensive air bladder is used as to dampen the vibrations encountered. As the loads placed on the bladder are large, the bladders must be designed to accept a large amount of compressive force when they are inflated without causing a blow out. This requires expensive bladders. Furthermore, the axle is connected to the air-suspension system using U-bolts that are secured through plates bolted to support arms. As the trailer is used on rougher surfaces, vibrations in the trailer often loosen the secure fit achieved by the U-bolts, resulting in a loosening of the axle, which is undesirable for a number of reasons that will be understood by those skilled in the art.
It is, therefore, desirable to provide a mechanism to allow owners of conventional trailers to obtain the benefits of an air suspension system for existing trailers.